With the emergence of the electric car, people start questioning the environmental impact of electric cars, in particular the CO2 emissions. Below you will find an article, based on scientific research, on the CO2 emissions of electric cars and how they compare to gasoline and diesel cars.

WTW, WTT en TTW

When CO2 emissions are discussed, often the following abbreviations are used: WTW, WTT and TTW. Figure 1 shows what each abbreviation stands for.

CO2 emissions electricity, gasoline and diesel

CO2 emission factors are factors that are used to calculate the CO2 emissions for organisations and activities. An example of a CO2 emission factor is the Well-to-Wheel (WTW) emission of 2.740 grams of CO2 for every liter of Dutch gasoline (co2emissiefactoren.nl, n.d.).

The Dutch website http://co2emissiefactoren.nl/ was founded by SKAO, Stimular, Connekt Milieu Centraal, the central government and various experts. This website contains a large database of CO2 emission factors. Table 1 shows the relevant CO2 emission factors for cars.

Table 1: Overview of relevant CO2 emission factors for cars

The Dutch grey energy is, for approximately 30%, generated by coal, the rest is generated by natural gas and nuclear power. The average Dutch energy mix is a mixture of, i.a., coal, natural gas, nuclear power, biomass, solar, wind and hydropower (CBS, February 2015).

CO2 emissions related to car usage

When the CO2 emissions of a car are calculated, usually only the direct emissions are being taken into account. The New European Driving Cycle (NEDC) only considers the direct emissions and therefore only the Tank-to-Wheel (TTW) emissions. This is the reason for fully electric cars to be publicized as zero-emission. In order to make a fair comparison between electric and fossil fuel cars, the indirect (WTT) emissions should be taken into account as well.

The EcoTest data is used for the electricity consumption. The EcoTest is performed in Germany and takes into account the charge loss of charging electric cars by reading out the used energy by the charger (EcoTest, n.d.). The consumption per 100 km for these electric cars, including charge loss, can be found in table 2.

Table 2: Energy consumption electric cars including charge loss

To calculate the CO2 emissions of the electric cars, the information in table 1 and table 2 can be combined. Table 3 provides an overview of the CO2 emissions and a comparison of the fuel consumption of gasoline and diesel cars to match the emissions of electric cars.

Table 3 shows the difference in CO2 emissions between electric cars and cars running on fossil fuel. The difference between grey and average energy is significant, but even electric cars using grey energy are causing less CO2 emissions than comparable cars on gasoline or diesel.

CO2 emissions life cycle car

The indirect and direct CO2 emissions related to usage of the car are not complete without taking into account the CO2 emissions that are caused by producing and recycling the car.

If 100% coal powered energy is used to charge the electric car, the electric car causes 4% less CO2 emissions compared to a similar gasoline or diesel car (TNO, 14 July 2014). Coal powered electricity causes 935 grams of CO2 per kWh (TNO, 14 July 2014), the Dutch energy mix causes 355 grams of CO2 per kWh (co2emissiefactoren.nl, n.d.).

Research from TNO shows that electric cars have less CO2 emissions than hybrid-cars and gasoline and diesel cars. The research takes the life cycle of the car into account, from producing to recycling and disposal. Looking at the life cycle of the car, an electric car causes, on average, 35% less CO2 emissions compared to a similar gasoline or diesel car (TNO, 7 April 2015).

Looking at the electricity production by source, it is safe to say The Netherlands has relatively grey, or dirty, electricity. Figure 4 provides an overview of the electricity production by source for Europe and the individual countries (Eurostat, 9 November 2015).

Figure 3: Breakdown of electricity production by source, 2014

It is safe to say The Netherlands is producing a relatively high percentage of its electricity by fossil fuels (mostly coal and natural gas) compared to the rest of Europe. This means that the CO2 emissions per kWh are relatively high in The Netherlands. Having this information, it can be concluded that electric cars are causing less CO2 emissions in Europe than in The Netherlands.

Conclusion

In The Netherlands the electric car, using grey electricity, is causing significantly less CO2 emissions than a similar gasoline or diesel car.

A point of discussion that is not yet discussed, is the CO2 emission factor for electricity that is reported by some organisations to calculate the CO2 emissions of electric cars. This CO2 emission factor is based on grey energy and therefore provides the highest possible CO2 emissions for electric cars. As mentioned before, grey energy comprises of coal, natural gas and nuclear power. Since the average energy mix is also comprised of renewable energy sources, using the emission factor for grey electricity is misleading. For gasoline and diesel there is no room for discussion, since there is (in essence) only one type of gasoline and one type of diesel. It is unfair and misleading to use the grey energy emission to calculate the CO2 emissions of an electric car. It is less unfair to use the CO2 emission of the average energy mix, although that is still not considering electric cars that only use renewable electricity.

Individuals who would like to calculate their CO2 emissions caused by the usage of their cars, are advised to use the CO2 emission that reported on their energy label. This CO2 emission is the most accurate since it comes directly from the supplier.

Who is the “supplier” in this last sentence of the conclusion: “Individuals who would like to calculate their CO2 emissions caused by the usage of their cars, are advised to use the CO2 emission that reported on their energy label. This CO2 emission is the most accurate since it comes directly from the supplier.”?

Thank you for your question! The supplier is the energy supplier (in Dutch: energieleverancier) that provides you with the electricity. They are the producer/supplier and are legally required to provide their customers information on the mix of energy sources that were used to produce the electricity.

Thanks. So that’s for information about the mix of energy sources in our electricity. But what about the emission numbers of the car? What is the best source for that information? I would *not* say the car supplier.

driving the electric car gives no direct co2 emission. Maybe the car-producer can give information about the energy they use to build the car.
But I think that’s not so importnant for getting a cleaner city-air.

Well, the kWh of energy used to produce the car is important, but the production of all the materials is also important (mining, transporting, disposal, etc). The first part of my blog/article explains briefly what the different types of emissions are about (WTW, WTT, TTW). The car producer is probably the best source for this information, although TNO has also included the production and recycling of the car in their research. I suggest reading the original research articles of TNO and others that I provided in the literaturelist, to get a better understanding of the emissions caused by the production and recycling of the cars. It is easier to focus on the emissions caused by using the car, therefore that forms the main part of my blog/article.

For direct emissions the NEDC test is used. Dieselgate is about software to identify the test and then perform differently than on the road. The emissions of production and recycling (if done by manufacturer) are reported by the manufacturer and this information is audited by independent organisations. For emissions caused by production and recycling the manufacturer is the best source.

Nice work!
I mostly side with the opinion that only grey energy should be used in calculating CO2 emissions for EVs because I consider the question best framed as one of marginal emissions. The main studies in the US performed by the national energy labs follow this approach.

Thank you Eric! The reason I use the average energy for The Netherlands is that this represents the electricity that comes out of a random socket. I did add the grey energy in the table to calculate the fuel economy of fossil fuel cars. TNO, in their reports, uses a CO2 emission factor for electricity that is closer to the grey energy emission. Using only grey energy does not take renewable energy sources into account. When I will update this blog, I will consider the different approaches again and maybe add some more scenarios for the different electricity sources. Too bad the reports of TNO are in Dutch. Hopefully I can find new reports in English for an update.

No doubt, this question of whether to include the clean energy on the grid in calculating EV emissions is a bit of a head scratcher. I decided on marginal emissions after I posed the question thus: if I leave my ICE at home and drive an EV, what is the source fuel ? Since more PV panels do not come online and the sun does not shine brighter or the wind blow harder for my trip, it follows that more fossil fuels are burned to supply the electricity required.

The reason I say “mostly” grey for EV is that in some areas (my Colorado is an example,) wind farms are not utilized for part of the time that they could be. So it is at least possible that increased demand will be supplied by otherwise dormant clean energy. It is a complicated topic due to politics, not science.

I will preface by saying I’m an EV owner, but what about the ‘mine to wheel’ emissions, if coal is used for electricity production? I have absolutely no idea how much energy it takes to produce and transport coal, but I don’t think it’s zero!

Sustainable mobility is the way, and electric cars are part of it! The environment is suffering because of traditional cars pollution, and the air is less and less breatheble, especially in big cities. We need to change our habits and choose a greener future!